Android中自带的view种类很多，但是有时候不能满足我们的需求，下面介绍一种自定义view的方法，实现了拖动矩形到屏幕任意位置的需求。
[图片] 程序截图
[代码] Activity.java
package com.zhuozhuo;
import android.app.Activity;
import android.os.Bundle;
public class CSDNActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
[代码] CustomView.java
package com.zhuozhuo;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
/**
* 自定义的view，需要覆盖onDraw()方法绘制控件，覆盖onTouchEvent()接收触摸消息
*/
public class CustomView extends View {
private static final int WIDTH = 40;
private Rect rect = new Rect(0, 0, WIDTH, WIDTH);//绘制矩形的区域
private int deltaX,deltaY;//点击位置和图形边界的偏移量
private static Paint paint = new Paint();//画笔
public CustomView(Context context, AttributeSet attrs) {
super(context, attrs);
paint = new Paint();
paint.setColor(Color.RED);//填充红色
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawRect(rect, paint);//画矩形
}
@Override
public boolean onTouchEvent (MotionEvent event) {
int x = (int) event.getX();
int y = (int) event.getY();
switch(event.getAction()) {
case MotionEvent.ACTION_DOWN:
if(!rect.contains(x, y)) {
return false;//没有在矩形上点击，不处理触摸消息
}
deltaX = x - rect.left;
deltaY = y - rect.top;
break;
case MotionEvent.ACTION_MOVE:
case MotionEvent.ACTION_UP:
Rect old = new Rect(rect);
//更新矩形的位置
rect.left = x - deltaX;
rect.top = y - deltaY;
rect.right = rect.left + WIDTH;
rect.bottom = rect.top + WIDTH;
old.union(rect);//要刷新的区域，求新矩形区域与旧矩形区域的并集
invalidate(old);//出于效率考虑，设定脏区域，只进行局部刷新，不是刷新整个view
break;
}
return true;//处理了触摸消息，消息不再传递
}
}
[代码] main.xml 布局文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<com.zhuozhuo.CustomView android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</LinearLayout>
